A vehicle seat according to Japanese Patent Application Laid-Open (JP-A) No. 2008-238969 is provided with a seat section and a seatback that is coupled to the seat section. The seatback includes a lower frame, with a first pin and a second pin provided to the lower frame. The seatback further includes a side frame, and a first through hole and a second through hole are formed through the side frame. The second through hole is in communication with an auxiliary hole portion, the auxiliary hole portion opening onto the side of the second through hole. The first pin is inserted into the first through hole, and the second pin is inserted into the second through hole, thereby coupling the side frame to the lower frame.
When an impact load in a vehicle rear direction is imparted to the seatback, the side frame rotates centered on the first pin, and an edge portion of the second through hole contacts the second pin at two connection portions of the second through hole and the auxiliary hole portion, and the auxiliary hole portion performs deformation so as to be pushed outwards by the second pin. The impact energy imparted to the seatback is expended as energy for deforming the auxiliary hole portion, thereby absorbing the impact load imparted to the seatback.
As described above, in such a vehicle seat, the edge portion of the second through hole contacts the second pin at the two connection portions of the second through hole and the auxiliary hole portion when impact load in the vehicle rear direction is imparted to the seatback, and the auxiliary hole portion is pushed outwards by the second pin. There might be therefore a possibility of the auxiliary hole portion being deformed even when the impact load imparted to the seatback is low. There is thus also the possibility that stably absorption of impact load imparted to the seatback may not be possible.
A vehicle seat according to Japanese National-Phase Application No. 2010-500213 is provided with a seat section structure. An adaptor is coupled to the seat section structure by a pivot and a fixing screw, and a backrest structure is coupled to the adaptor.
The adaptor is further provided with a hole into which the fixing screw is inserted. Cut-out portions are formed at specific intervals at a side portion of the hole, with connection portions configured between the hole and a cut-out portion, and between one cut-out portion and another cut-out portion.
The adaptor rotates centered on the pivot when an impact load in the vehicle rear direction is imparted to the backrest structure, and the connection portions between the cut-out portions make contact the fixing screw, such that the connection portions are rupture (deform). When one connection portion ruptures, the ruptured connection portion proceeds to contact the next inter-cut-out portion connection portion and ruptures the next connection portion. The impact energy imparted to the backrest structure is accordingly expended as energy for rupturing (deforming) each of the connection portions, enabling the impact load imparted to the backrest structure to be absorbed.
However, as described above, in this vehicle seat each of the connection portions are ruptured (deformed) discontinuously, so the impact load imparted to the seatback structure is absorbed discontinuously. Impact load can therefore not be absorbed efficiently.